Figure 2(a) show the temperature-dependent resistivity, which indicates an insulating ground state of the HSL. This insulating behavior in comparison is slightly stronger than the bilayer SL but clearly weaker than the single-layer SL, suggesting that the conduction of the HSL cannot be simply viewed in a parallel-resistor-like picture where the monolayer and bilayer slabs host conduction completely independently. In other words, the finite tunneling across the STO spacer necessarily contributes to the total bandwidths and the final gap sizes of all the SLs [1]}, [2]}. Note that the HSL is different from both the monolayer and bilayer SLs in that the charge is now hopping between two dissimilar slabs. If the electronic structures of the two slabs are non-degenerate and they have different individual gap sizes, the inter-slab hybridization of the HSL will end up being suppressed from that of a uniform SL, which could account for the observed intermediate strength of the insulating behavior [3]}.
